DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 131256
SWODY1
SPC AC 131253

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0753 AM CDT SAT SEP 13 2008

VALID 131300Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM E TX/LA INTO SRN AND ERN
MO...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE UPR OH VLY...

...SYNOPSIS...
HRCN IKE EXPECTED TO CONTINUE GENERALLY N ACROSS E TX TODAY BEFORE
ACCELERATING NE ACROSS AR TONIGHT/EARLY SUNDAY AS SYSTEM BEGINS TO
INTERACT WITH PROGRESSIVE TROUGH OVER THE NRN PLNS. THE PLNS TROUGH
IS COMPOSED OF TWO MAIN SHORTWAVE FEATURES...THE LEAD ONE OF WHICH
IS NOW OVER SD/NEB. THIS IMPULSE SHOULD TURN NE INTO MN LATER TODAY
...AND REACH SRN ONTARIO EARLY SUNDAY...AS ASSOCIATED SFC WAVE
TRACKS FROM IA TO N OF LK HURON.

...IKE...
GIVEN EXPANSIVE NATURE/STRONG WIND FIELD WITH IKE...EXPECT STRONG
LOW LVL SHEAR TO DEVELOP N ACROSS E TX AND LA TODAY...AND N/NE INTO
FAR SE OK AND MUCH OF AR LATE TODAY/TONIGHT. THUS...DESPITE OVERALL
WEAK LOW LVL BUOYANCY...A THREAT WILL EXIST FOR ISOLD TORNADOES WITH
ANY SUSTAINED CONVECTION FORMING WITHIN THE ERN AND NERN PARTS OF
SYSTEM. THIS THREAT SHOULD BE GREATEST IN AREAS OF STRONGEST SFC
HEATING...I.E. ALONG AN ARC FROM CNTRL LA NNW TOWARD THE ARKLATEX.
THE TORNADIC POTENTIAL MAY INCREASE TONIGHT/EARLY SUNDAY IN VERY
MOIST ENVIRONMENT OVER CNTRL/NRN AR AND SRN/ERN MO AS ACCELERATION
OF IKE ENHANCES ISALLOBARIC BACKING OF NEAR-SFC FLOW.

...OH VLY/LWR GRT LKS...
PLUME OF RICH TROPICAL MOISTURE /WITH PW AOA 2 INCHES/ WILL PERSIST
FROM THE MID MS VLY TO THE LWR GRT LKS THIS PERIOD...AHEAD OF WEAK
FRONTAL SYSTEM ASSOCIATED WITH IA SFC WAVE AND NRN PLNS TROUGH.
BAND OF MODERATE TO SEASONABLY STRONG SW FLOW WILL ACCOMPANY THE
MOISTURE PLUME IN WAKE OF WARM FRONT NOW MOVING ENE ACROSS THE UPR
OH VLY. FORCING FOR ASCENT IN WARM SECTOR EXPECTED TO REMAIN FAIRLY
WEAK...DOMINATED BY UPR DIVERGENCE WITH JET ENTRANCE REGION IN NY/SW
QUEBEC. NEVERTHELESS...COUPLED WITH SFC HEATING AND WEAK
CONVERGENCE/DIFFERENTIAL HEATING IN WAKE OF WARM FRONT...SETUP COULD
SUPPORT A RENEWED ROUND OF STORMS THIS AFTN...MAINLY ACROSS PARTS OF
LWR MI/NRN IND/NRN OH AND WRN PA.

WEAK MID LVL LAPSE RATES SHOULD TEMPER OVERALL SEVERITY OF
STORMS...AND VEERED SFC FLOW SHOULD LIMIT TORNADO THREAT IN WARM
SECTOR. BUT STRENGTH OF MEAN FLOW AND HI PWS COULD SUPPORT A FEW
BOWING SEGMENTS WITH LOCALLY DMGG WIND IN THE WARM SECTOR...AND
ISOLD TORNADOES COULD OCCUR CLOSER TO THE WARM FRONT IN SRN MI/NRN
OH/WRN PA.

FARTHER SW...EXPECT STORMS TO INCREASE IN COVERAGE THIS EVE AND
TONIGHT ALONG COLD FRONT FROM CNTRL MO INTO CNTRL IL AS WIND
FIELD/LOW LVL CONVERGENCE AND UPR LVL DIVERGENCE INCREASE WITH THE
APPROACH OF IKE. ISOLD TORNADOES AND EXCESSIVE RAINFALL COULD POSE
DUAL THREATS FROM SLOWLY-PROGRESSIVE...REGENERATIVE STORMS.

..CORFIDI/HURLBUT.. 09/13/2008

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